Comb sources and multi-frequency lasers are key candidates for enabling the move to lower costs for optical communication systems. As is well-known in the art, a comb generator allows for a given laser device to emit at a number of spaced-apart, separate wavelengths (“comb lines”). Compared to a conventional transponder architecture that utilizes a separate tunable laser with each modulator, the introduction of a comb source allows for a single tunable laser source to be shared among several modulators, each modulator utilizing a separate one of the comb lines.
While the utilization of a comb source is beneficial, the number of simultaneously lasing wavelengths depends primarily on the gain bandwidth of the specific material used to create the comb and fixed cavity parameters associated with the laser. To date, mode-locked lasers (MLLs) have typically been able to control the mode spacing (i.e., separation between emission lines) and not the actual number of comb lines that are generated. As a result, it is typical that a substantially larger number of comb lines are generated than required for a specific application, sacrificing power efficiency and increasing noise present in the optical communication system.